S. Simon

Babeş-Bolyai University, Klausenburg, Cluj, Romania

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Publications (158)219.38 Total impact

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    ABSTRACT: Nanoencapsulation of pharmaceutically active natural compounds into porous systems through sol–gel method leads to new drug delivery materials with sustained release behaviour of the entrapped pharmaceuticals. Properties of inorganic sol–gel-derived silica microparticles loaded with cotton (Gossypium hirsutum) seeds extract are reported. Xerogels obtained by heat or freeze drying were investigated by X-ray diffraction, dynamic light scattering, differential thermal analysis (DTA)/thermogravimetric analysis (TGA), UV–Vis and fluorescence spectroscopy. Effects of drying process on both silica particles and plant extract were evaluated. In vitro release was studied in release media with pH 1.1 and 7.4. The investigated biocomposite systems display a biphasic release profile wherein the diffusion prevails over the dissolution.
    Journal of Sol-Gel Science and Technology 08/2015; DOI:10.1007/s10971-015-3828-8 · 1.55 Impact Factor
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    ABSTRACT: A comparative study of three phosphosilicate gels of the 90SiO2-10P2O5 composition obtained from tetraethoxysilane and three phosphorous precursors: triethylphosphate (TEP), triethylphosphite (TEPI) and H3PO4 is performed. 29Si and 31P Magic Angle Spining NMR, X-ray Photoelectron, X-ray Fluorescence and Raman spectroscopies as well as TG analysis are used in order to establish phosphorous precursors and annealing influence on composition and structure of the outcome materials. Unlike the three dimensional silicate network made of Si(OSi)x(OH)4-x species, unreacted TEP (100 % Q1 condensed phosphorous units) from TEP derived gel and a large amount of isolated phosphorous species (39.7 % Q0) in the H3PO4 derived gel are identified. Annealing at 700 C of the three gels give similar structure with the 90SiO2-10P2O5 glass, excepting the triethylphosphate derived glass that has a much lower P content. Thus, the H3PO4 derived glass at 700 and 1000 C shows 1.89 and 1.94 times higher P2O5/SiO2 ratios than in the case of the TEP derived one.
    Journal of Molecular Structure 04/2015; 1086:161-171. DOI:10.1016/j.molstruc.2015.01.012 · 1.60 Impact Factor
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    ABSTRACT: Well-defined calcium molybdate (CaMoO4) and hydroxyapatite (HAP) nanocrystals were developed by thermal treatment on the surface of a SiO2–CaO–P2O5–MoO3 amorphous precursor synthesised at room-temperature by sol–gel route. The structural and morphological characterisaions were performed by several techniques: energy dispersive X-ray spectroscopy, thermal analyses (DTA/TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, electron paramagnetic resonance. Complementary, Fourier transform infrared and Raman spectroscopies provided a clear picture regarding the short range order structure, emphasising beside the CaMoO4 phase development, the presence of HAP nanocrystals. The vibrational spectroscopic techniques proved to be valuable tools for evidencing very small HAP nanocrystallites that cannot be clearly observed by XRD and TEM analyses.
    Journal of Materials Science 01/2015; 50(2). DOI:10.1007/s10853-014-8615-3 · 2.37 Impact Factor
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    ABSTRACT: Gossypol is a polyphenolic compound with a wide range of therapeutic properties. The incorporation of gossypol in a porous gadolinium-silica matrix was considered for both therapeutic effect and contrast in magnetic resonance imaging. The purpose of the study was to evaluate gossypol loading in silica-gadolinium particles prepared at different pH values, as a first step in designing new theranostic (therapeutic and diagnostic) compounds. Silicagadolinium particles of 98SiO2�2Gd2O3 (mol%) composition were prepared following the sol–gel route. The structure of the particles and their loading with gossypol were investigated by X-ray diffraction, dynamic light scattering, Brunauer–Emmett–Teller analysis, differential thermal analysis, Fourier transform infrared spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy. All results confirmed the highest loading of gossypol on the surface of the particles synthesised at lower pH. The potential application in magnetic resonance imaging (MRI) of silica-gadolinium particles loaded with gossypol was tested through MRI measurements that showed improved contrast properties compared with the pristine silica-gadolinium particles.
    Journal of Sol-Gel Science and Technology 12/2014; 72(3). DOI:10.1007/s10971-014-3482-6 · 1.55 Impact Factor
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    ABSTRACT: The synthesis procedure represents a key aspect in designing the physical and chemical prop-erties of gold nanoparticles. The current study pro-poses a simple approach for gold nanoparticles synthesis using non-thermal plasma. The novelty of the setup consists in producing an in-liquid plasma discharge in argon bubbles that are externally gener-ated in the solution exposed to treatment. Because plasma is the source of active species which are directly involved in gold reduction, no additional reducing agent was necessary. Collagen protein was used as capping agent. A plasma treatment of 10 min is sufficient for obtaining stable colloidal solutions with UV-Vis absorption maximum at 530 nm. Trans-mission electron microscopy images revealed prepon-derant spherical nanoparticles with dimensions in the range of 6–20 nm. The method of synthesis distin-guishes by its good reproducibility, facility, efficiency, and ability to generate stable colloidal nanoparticles after several minutes of plasma exposure.
    Journal of Nanoparticle Research 08/2014; 16(10). DOI:10.1007/s11051-014-2633-6 · 2.28 Impact Factor
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    ABSTRACT: The “build-up” methodology of a composite photocatalyst is a critical issue regarding the showed photocatalytic performance, including the formation of intermediates. To investigate this issue P25/WO3/Au composites were obtained by impregnation (WO3) and subsequent photoreduction (Au) with UV or visible light. The obtained composites’ photocatalytic activity and intermediate formation profiles were evaluated using phenol as a model pollutant. XPS/UPS and DRS methods were used to uncover local coordination, surface chemistry (of the different types of atoms (Ti, W, O and Au) and the band-structure (band-gap, possible electron transitions) of the obtained nanomaterials. The intermediates’ evolution profile and structural peculiarities were successfully correlated and it was shown that each minor structural (bulk or surface) change has a significant impact on the photocatalytic activity and intermediate formation dynamics.
    Applied Catalysis B Environmental 04/2014; 147:508-517. DOI:10.1016/j.apcatb.2013.09.019 · 6.01 Impact Factor
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    ABSTRACT: Nanostructured hydroxyapatite (HA)-iron oxide composites obtained by a wet-chemical method through co-precipitation were investigated with respect to the changes induced in the samples structure by progressive addition of iron, by thermal treatments carried out at 450 oC, 550 oC and 700oC, and by incubation in simulated body fluid. The structural changes were analysed by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and magic angle spinning nuclear magnetic resonance (MAS-NMR). After heat treatments, crystalline HA was developed in all samples, even in larger amount in those with iron, showing that iron acts as catalyser for HA development. The MAS-NMR results show as well that only a part of the iron atoms are uniformly incorporated in the HA structure by replacing of calcium. EPR results support that an important part of iron atoms are disposed in regions rich in iron that behave like superparamagnetic or magnetic particles distributed in HA matrix. The analyses carried out on 550 oC treated samples, after three days of immersion in SBF, point out a decrease of HA crystallites size and the appearance on particles surface of a new amorphous calcium phosphate layer.
    Ceramics International 03/2014; 40(7). DOI:10.1016/j.ceramint.2014.03.124 · 2.09 Impact Factor
  • O Ponta · R Ciceo-Lucacel · A Vulpoi · T Radu · S Simon
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    ABSTRACT: The study is focused on synthesis, investigation of the structural and morphological changes induced by MoO3 addition and thermal treatment, as well as in vitro characterization of a new sol-gel derived SiO2 -CaO-P2 O5 bioactive materials. The obtained systems are composite materials consisting of nanocrystalline apatite, bioactive glass and CaMoO4 nanoparticles, which are of interest for both regenerative medicine and specific medical applications of the releasable molybdenum ions. The changes induced by the thermal treatments and MoO3 addition with respect to the structure and morphology were completed using DTA\TGA, XRD, SEM, EDX, XPS, FTIR, EPR and BET. The biological performance of these materials was evaluated in vitro by performing bioactivity and biocompatibility tests. The bioactive properties in terms of HAp layer formation on the biomaterial surface after SBF immersion were studied by XRD and SEM. In order to establish their biocompatibility, the biomaterials surface was functionalized with protein and the resulted sample was investigated using SEM, FTIR and XPS. The obtained results suggest that the addition of molybdenum oxide in proper concentration improves the biocompatibility in terms of enhancement of protein adherence on Si-Ca-P surface due to CaMoO4 crystalline phase development and does not inhibit bioactivity.
    Journal of Biomedical Materials Research Part A 10/2013; DOI:10.1002/jbma.34989 · 3.37 Impact Factor
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    ABSTRACT: The biocompatibility of nanostructured titanosilicate microspheres with different Ti/Si ratios was evaluated by probing the affinity of horse haemoglobin (Hgb) towards the samples surface, in terms of quantitative and conformational changes analysis. The samples morphology before and after protein adsorption was evaluated by Scanning Electron Microscopy (SEM). X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) on spin labeled protein and Fourier Transform Infrared (FTIR) spectroscopies were further used to achieve information concerning both the amount of attached haemoglobin and its secondary structure modifications upon adsorption. The obtained results suggest that nanostructured titanosilicate microspheres present a friendly surface for protein adsorption and an enhanced protein adherence with increase of silica content.
    Journal of Molecular Structure 07/2013; 1044. DOI:10.1016/j.molstruc.2013.01.026 · 1.60 Impact Factor
  • F. Taloş · M. Senilă · T. Frentiu · S. Simon
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    ABSTRACT: The dissolution and surface layer changes of new xTiO2(100 − x)[4SiO2·CaO·0.3P2O5] sol–gel derived xerogels (0 ⩽ x ⩽ 20 mol%) have been investigated in Kokubo’s simulated body fluid (SBF). The ionic leaching rate was analysed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). ICP-AES results showed a relatively fast dissolution of titanium free sample, with a high release of phosphorous and calcium ions in the first hour of incubation while the release of silicon ions continuously increased up to 6 h of immersion. The titanium dioxide addition up to 20 mol% differently influences the release of phosphorus, calcium and silicon ions, i.e. TiO2 strongly stabilises the phosphorus ions, to a lesser extent the calcium ions, and has almost no effect on the silicon ions release. The structural changes were evaluated using X-ray powder diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The XRD results show that all samples remain mainly amorphous after immersion in SBF. The changes occurred in the surrounding of phosphorous and silicon ions are well reflected in FTIR spectra and they were correlated with the samples stability in SBF.
    Corrosion Science 07/2013; 72:41–46. DOI:10.1016/j.corsci.2013.03.003 · 3.69 Impact Factor
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    ABSTRACT: Titania/tungsten (VI) oxide/noble metal (gold and platinum) composites were obtained by the means of selective noble metal photodeposition on the desired oxide’s surface (either on TiO2 or on WO3). The noble metal particles’ localization was proved by SEM-EDX, while their size with DRS and TEM. The influence of the noble metal nanoparticles’ position was investigated successfully on the light absorption properties, photocatalytic activity toward oxalic acid and photocatalytic hydrogen production. Major differences were observed in the photocatalytic performance of the catalysts in which only the position of the noble metal was changed. Consequently, highly active composites were obtained, that surpassed the reference catalysts’ (TiO2(Au), TiO2(Pt), WO3(Au), WO3(Pt)) oxalic acid degradation yield and were also quite active for photocatalytic hydrogen production
    Catalysis Today 06/2013; 208:19-27. DOI:10.1016/j.cattod.2012.09.038 · 3.31 Impact Factor
  • S. Simon · M. Todea
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    ABSTRACT: Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopic data obtained for iron doped silica-bismuthate glasses were used to investigate the changes induced in the local structure of samples as the ratio between Bi2O3 and SiO2 content changes from 3 to 0.66. The environment of constituent cations was investigated both in vitreous and partially crystallized samples of same composition. Progressive substitution of Bi2O3 by SiO2 contributes to the structural relaxation of vitreous network and enhances glass stability. By crystallization heat treatment the structural units appear to be more uniform as it results from the narrowing of corresponding IR bands and EPR lines. FTIR data show that more affected by composition and heat treatment is the environment of bismuth than that of silicon. EPR data indicate an ordering tendency with SiO2 content in glasses, while in vitroceramics the iron environment is much uniform in samples with less SiO2 content, where Bi12SiO20 phase is developed.
    Journal of Non-Crystalline Solids 04/2013; Journal of Non-Crystalline Solids:2947-2951. DOI:10.1016/j.jnoncrysol.2006.04.022 · 1.77 Impact Factor
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    M. Todea · B. Frentiu · R.F.V. Turcu · P. Berce · S. Simon
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    ABSTRACT: Aluminosilicate microspheres obtained by spray drying were investigated in prospect of their potential biomedical applications. The as-prepared microspheres are amorphous. TEM and AFM were used to examine the morphology of the samples before and after immersion in simulated body fluid (SBF). The local structure changes as a function of microspheres composition and due to their immersion in SBF were investigated by 29Si and 27Al MAS–NMR. After SBF immersion, the silica network partially depolymerised by hydration/hydroxylation and the completely changed aluminium environment suggest a phylosilicate-like structure. 31P MAS–NMR analysis evidenced phosphorus ions incorporated in a new crystalline phase developed during SBF immersion.Highlights► Aluminosilicate microspheres less than 20 μm were prepared by spray drying. ► Microspheres structure is modified after immersion in simulated body fluid (SBF). ► Silica network is partially depolymerized by hydration/hydroxylation in SBF. ► After SBF immersion the aluminum environment is completely changed. ► Apatite type nanocrystals grown on microspheres in SBF mark their bioactivity.
    Corrosion Science 04/2013; Corrosion Science, 54:299-306. DOI:10.1016/j.corsci.2011.09.032 · 3.69 Impact Factor
  • M.Todea · E. Vanea · S. Bran · P. Berce · S. Simon
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    ABSTRACT: The study aims to characterize surface properties of aluminosilicate microspheres incorporating yttrium, with potential biomedical applications. Micrometric particles of spherical shape were obtained by spray drying method. The behavior of aluminosilicate microspheres without yttrium and with yttrium was investigated under in vitro conditions, by seven days incubation in simulated body fluid (SBF). The surface elemental composition and the atomic environments on outermost layer of the microspheres, prior to and after incubation in SBF were evaluated by X-ray photoelectron spectroscopy (XPS) in order to investigate their bioactivity. The results were analyzed to underline the effect of yttrium addition on surface properties of the aluminosilicate microspheres and implicitly on the behavior of the samples in simulated body environments.
    Applied Surface Science 04/2013; Applied Surface Science 270 (2013) 777– 783. DOI:10.1016/j.apsusc.2013.01.178 · 2.54 Impact Factor
  • T Radu · M T Chiriac · O Popescu · V Simon · S Simon
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    ABSTRACT: The behavior of yttria-alumina-silica spray-dried microspheres was investigated in vitro on a human keratinocyte cell line, first to exclude their cytotoxicity. The HaCaT cells were chosen due to their well-characterized phenotype and their phagocytic ability. Microscopic analysis and cell viability tests showed no negative effect of the microspheres on cells morphology and behavior. Scanning electron microscopy and transmission electron microscopy results evidenced the cellular internalization of the microspheres at 48 h after their incubation with cultured cells. The shape, size distribution, structure, composition, and chemical states of the elements on samples surface were analyzed by SEM, transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, because these properties could influence their internalization by cells. The yttrium distribution on the microspheres surface was indicated by fluorescence microscopy imaging. The microspheres dimension and shape inside the cells was in accordance with their dimension and shape before incubation. The microspheres seemed captured and engulfed by the cells in native form and appeared resistant to degradation over the first 48 h. Most of the analyzed cells took up more microspheres, suggesting that the microspheres were actively phagocytosed by the cells and accumulated within the cytoplasm. X-ray photoelectron spectroscopy results on Al and Si atomic environments denoted Al-O-Si crosslinks, which improve the surface protection to corrosion. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.
    Journal of Biomedical Materials Research Part A 02/2013; 101A(2). DOI:10.1002/jbm.a.34320 · 3.37 Impact Factor
  • Talos F. · Vulpoi A. · Ponton A. · Simon S. · Dudea D. · Bran S.
    Digest Journal of Nanomaterials and Biostructures 01/2013; 8:219-225. · 1.12 Impact Factor
  • O. Ponta · E. Vanea · A. Cheniti · P. Berce · S. Simon
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    ABSTRACT: The aim of the present study was to synthesize by spray drying titanosilicate microspheres of less than 5 μm in diameter and to induce by thermal treatment the growth of nanocrystalline phases in amorphous matrices. The microspheres obtained by this process belong to the xTiO2:ySiO2 system, with x:y ratios of 1:2, 1:1 and 2:1, doped with 1% Gd2O3. Anatase and rutile nanocrystals were developed by increasing the calcination temperature from 700 to 1100 °C, and both are desired phases concerning their applications. Structural and surface characterization before interaction with biological and/or environmental media are an important issue for the expected behaviour in such milieus. The changes induced by the thermal treatments with respect to structure, morphology and Ti/Si ratio on the surface of the samples were investigated using thermogravimetrical (TGA), differential thermal analyses (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Surprisingly, for as-prepared microspheres the surface atomic composition relative to Ti and Si is quite similar for all three systems, while for the heat treated samples the Si content increases, that reflects that the developed titania nanocrystals are covered by a thin layer of amorphous silica.
    Materials Chemistry and Physics 08/2012; 135(2-3):863–869. DOI:10.1016/j.matchemphys.2012.05.071 · 2.13 Impact Factor
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    ABSTRACT: A comprehensive analysis of heterogeneous nanostructures based on TiO2 aerogels and Ag nanoparticles (NPs) is reported herein. The experimental techniques engaged along this study enable a multi-scale approach for the characterization of this composite system. The results clearly indicate that an increase of the Ag amount within the porous structure of TiO2 nanograins leads to a lower dispersion of Ag on the support. For a higher Ag global amount, the proportion of encapsulated NPs increases considerably, reducing in this manner the amount of accessible Ag. The effect of the thermal treatment on such nanostructures has been evaluated as well. The specimen annealing appears to induce a considerable diminution of the microporosity, finding that is in good agreement with the results obtained by measurement of the specific surface area of the TiO2 grains. The annealing also changes the microstructural characteristics of these nanostructures, as expected. More specific, it leads to an enhanced degree of encapsulation of Ag NPs, which as consequence become considerably less accessible. Being focused on the analysis of porous nanocomposites with specific properties, the current investigation aims as well at emphasizing the remarkable potential of electron tomography, a technique that can be successfully employed for precise analysis of three dimensional nanostructures.
    RSC Advances 05/2012; 2(12):5358-5369. DOI:10.1039/C2RA20568H · 3.84 Impact Factor
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    D. Trandafir · M. Vasilescu · S. Simon
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    ABSTRACT: Noncrystalline and nanocomposite materials of (1-x)SiO2�xGeO2 system, with Si:Ge ratio from 8:1 to 2:1(x = 0.111; 0.142; 0.2; 0.333), initially obtained by sol–gel method, were characterized by thermal analyses, X-ray diffraction, nuclear magnetic resonance and Raman spectroscopy. According to DTA and XRD results, the noncrystalline state of the as-prepared samples is stable up to 1,000 �C and only after 30 min heat treatment at 1,200 �C the samples become partial crystalline, due to development of cristobalite and quartz nanocrystals. Solid-state 29Si MAS-NMR was employed in order to characterize the local structure around silicon as a function of composition and thermal history of the samples. The NMR data indicate the presence of Q2, Q3 and Q4 units in all samples. The fraction of the highly interconnected SiO4 tetrahedra increases both with germanium content and with annealing temperature. The Raman spectroscopy results evidence structural changes related to silicon- and germanium-oxygen units but also to their interconnection, that depend on Si:Ge ratio and annealing temperature.
    Journal of Sol-Gel Science and Technology 05/2012; 63(3):425-434. DOI:10.1007/s10971-012-2804-9 · 1.55 Impact Factor
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    C. Gruian · A. Vulpoi · H-J. Steinhoff · S. Simon
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    ABSTRACT: Functional protein adsorption at liquid–solid interfaces has been intensively studied in the last years, however it is difficult to evidence directly conformational changes of the protein which are likely to appear upon adsorption. Spin labeling in combination with Electron Paramagnetic Resonance (EPR) spectroscopy was applied in this study to investigate adsorption of horse methemoglobin to bioactive glass (BG) similar in composition with 45S5 Bioglass®. X-band cw-EPR spectra of spin labeled methemoglobin in solution were compared to those obtained after adsorption on bioactive glass surface (functionalized and non-functionalized with glutaraldehyde), to extract information of the structure and dynamics in the vicinity of position β-93. The concentration of methemoglobin adsorbed on BG substrate was determined from the intensity of cw-EPR spectra and correlated with images obtained by Scanning Electron Microscopy (SEM). Line shape analysis of the EPR spectra revealed that ionic strength does not induce significant conformational changes in the protein structure upon adsorption, however, the chemical treatment applied to the bioactive glass surface positively influences protein adsorption.
    Journal of Molecular Structure 05/2012; 1015:20. DOI:10.1016/j.molstruc.2012.01.045 · 1.60 Impact Factor